std.sumtype?

[jmh530]

On Monday, 22 March 2021 at 21:43:58 UTC, Paul Backus wrote:
> On Monday, 22 March 2021 at 19:24:54 UTC, JN wrote:
>> Does anyone know if it would be possible to make it support 
>> (it doesn't support it now) this kind of syntax:
>>
>> Temperature t1 = Fahrenheit(98.6);
>> isFahrenheit(t1); // works
>> isFahrenheit(Fahrenheit(98.6)); // doesn't work :(
>
> You can do this by adding an additional overload to 
> isFahrenheit:
>
> bool isFahrenheit(T)(T t)
>     if (staticIndexOf!(T, Temperature.Types) >= 0)
> {
>     return is(T == Fahrenheit);
> }
>
> bool isFahrenheit(Temperature temp)
> {
>     // Forward to template overload
>     return temp.match!isFahrenheit;
> }

What about something like
Fahrenheit t2 = t1.to!(BaseTypeOf!(typeof(t1)));
that could then be put into its own function.